What is diabetes and how is it diagnosed?


Diabetes is a disease characterized by elevated blood sugar levels. It is extremely common, affecting more than 400 million people worldwide, many of whom aren’t even aware that they have it (1).

If you have diabetes, your blood sugar rises higher than it should after eating a balanced meal. What’s more, it is typically higher than it should be most of the day, including overnight and first thing in the morning.

Diabetes can be diagnosed in one of four ways:

  1. Fasting plasma glucose test: Measures your blood sugar after you’ve gone without food for a minimum of 8 hours.

  2. Random blood glucose test: Measures your blood sugar at any time of day, whether you’ve eaten recently or not.

  3. Oral glucose tolerance test: Measures your blood sugar at one-hour intervals for up to three hours after you consume a sugary liquid.

  4. Hemoglobin A1c: Reflects a 3-month average of your blood sugar levels.

Prediabetes is considered a “stepping stone” towards diabetes. It is diagnosed if your blood sugar is higher than normal but not high enough to meet the criteria for diabetes.

However, prediabetes may progress to diabetes over time, especially if blood sugar remains elevated.

Moreover, prediabetes is increasing even faster than diabetes. It’s estimated that in the US alone, 37% of people over 20 and 51% of people over 65 have prediabetes. By 2030, experts predict that the global number of people with prediabetes will reach a staggering 471 million (2).

Here is a chart showing the A1c, fasting blood sugar and oral glucose tolerance test values used to diagnose diabetes and prediabetes:

(Photo source: healthy-ojas.com)

In addition, a random blood sugar of 200 mg/dL (11.1 mmol/L) or above can be used to diagnose diabetes if other symptoms are present. These symptoms include:

  • Excessive urination: When there is too much sugar in your blood, your kidneys flush it out of your system by increasing urine production.

  • Excessive thirst: Frequent urination leads to dehydration and causes you to feel extremely thirsty. In fact, you may feel unable to quench your thirst no matter how much you drink.

  • Increased hunger: Due to hormonal imbalances, your body has problems converting the food you eat into energy. Therefore, it sends signals that drive you to eat.

  • Unexplained weight loss: Despite having a good appetite, you may lose weight because your body isn’t able to absorb nutrients from the food you eat.

  • Fatigue: Because your cells can’t access the fuel they need to function properly, you feel tired, weak and exhausted even when doing very little physical activity.

Although these symptoms are often present at diagnosis — and may be the reason for going to the doctor in the first place — they are also seen in

uncontrolled diabetes. Indeed, they can occur anytime blood sugar is too high, whether you’ve had diabetes for a few weeks or many years.

Living with elevated blood sugar can increase your risk for developing all sorts of serious health problems over time, including:

  • Heart attack

  • Stroke

  • Kidney disease

  • Nerve damage

  • Blindness

  • Gum disease

What’s more, high blood sugar can speed up the aging process by damaging collagen, the main protein in your skin. If your diabetes is poorly controlled, you’re likely to develop wrinkles and sagging skin at an earlier age (3).

In addition, recent research has shown that even prediabetic-range blood sugar may cause many of the same problems seen in diabetes, including increased risk of heart disease and other conditions (4, 5).

Achieving and maintaining blood sugar levels in or near the normal range is extremely important for avoiding these complications.

How diabetes develops and progresses

You may have heard that diabetes is a disease in which the body can’t process sugar or carbs normally. This is certainly true.

However, the disease is actually quite complex and involves an inability to regulate blood sugar due to impaired hormone production or function.

The main hormones involved in regulating blood sugar are insulin and glucagon.

  • Insulin: A hormone produced by the beta cells of your pancreas that signals your cells to take up sugar, or glucose, from the bloodstream.

  • Glucagon: A hormone produced by the alpha cells of your pancreas that signals your liver to release sugar into the bloodstream.

The cells in your body use sugar (glucose) as fuel. This includes the cells in your muscles, brain, heart and all your other organs.

Your liver stores sugar in the form of glycogen, which is made up of chains of smaller sugar units.

If your blood sugar is low, your pancreas secretes glucagon, which tells the liver to break down glycogen into sugar and release it into the bloodstream. This process is called glycogenolysis.

When blood sugar rises, your pancreas secretes insulin, which acts as a key that allows sugar to move from the bloodstream into your cells. In addition, insulin signals your liver to take up sugar from the blood and store it as glycogen, particularly after a meal.

What happens in diabetes?

Normally, the beta cells of your pancreas produce small amounts of insulin throughout the day and night in order to keep your blood sugar in a very narrow range of about 80-100 mg/dL (4.4-4.6 mmol/L).

However, in prediabetes and the early stages of type 2 diabetes, your cells don’t respond appropriately to insulin’s action. This is known as insulin resistance.

Essentially, the lock-and-key mechanism is broken, so sugar can’t enter your cells efficiently. Therefore, blood sugar remains elevated, even though there is plenty of insulin available.

(Photo source: epimigrant.eu)

The pancreas responds to this by producing more insulin in an attempt to drive the sugar out of the bloodstream and into the insulin-resistant cells. This cycle is repeated over and over on a daily basis, especially after meals, when blood sugar levels are highest.

As this process continues, the cells become progressively more resistant to insulin, which increases the demands on the pancreatic beta cells to produce it in even greater quantities.

Over time, the beta cells lose their ability to make enough insulin to compensate for the insulin resistance. This is known as beta cell failure.

In addition to the beta cells becoming worn out from producing so much insulin, they can also become damaged by prolonged exposure to high blood sugar, which is referred to as glucose toxicity (6 ,7, 8).

Once beta cell failure occurs, insulin injections are typically prescribed.

Importantly, this doesn’t happen to every person with diabetes. However, chronically high blood sugar levels greatly increase the likelihood that your pancreas will eventually no longer produce enough insulin.

On the other hand, taking steps to get your blood sugar under control as early as possible can help protect the health of your beta cells, reduce insulin resistance and potentially decrease your need for diabetes medication.

Which type of diabetes do you have?

There are 4 major types of diabetes, and although they share some similarities, they are actually very different diseases.

  1. Type 1 diabetes

  2. Type 2 diabetes

  3. LADA (Latent Autoimmune Diabetes in Adults)

  4. Gestational diabetes

It’s important to know which kind of diabetes you have in order to understand the benefits and limitations of making diet and other lifestyle changes.

Type 1 diabetes

Type 1 diabetes is also called insulin-dependent diabetes. It was previously known as “juvenile diabetes” because it is typically diagnosed in childhood.

However, type 1 diabetes can be diagnosed at any time from infancy to old age, although it occurs much more often in younger individuals. In fact, there have been rare cases of people developing type 1 diabetes in their 90s (9).

People with type 1 diabetes are unable to produce insulin due to an autoimmune process that destroys their pancreatic beta cells. Therefore, they must inject insulin several times a day in order to keep blood sugar under control (10).

However, their insulin needs can be minimized by making certain lifestyle changes.

Type 2 diabetes

Type 2 diabetes is also known as non-insulin-dependent diabetes. It is by far the most common form of diabetes. Indeed, 90% of all people with diabetes have type 2 (11).

Up until 30 years ago, type 2 diabetes was commonly referred to as adult-onset diabetes because it was virtually unheard of in childhood.

However, this has definitely changed in recent years.

As a result of the dramatic increase in obesity, high-carb processed food intake and inactivity among children and adolescents, type 2 diabetes diagnosis now accounts for up to 45% of all new cases of diabetes diagnosed in childhood (12).

As discussed in the previous section, type 2 diabetes is characterized by insulin resistance that forces the pancreas to increase production of insulin to maintain blood sugar control.

If you were diagnosed with type 2 diabetes, your doctor may have prescribed one or more oral medications for you to take. Insulin is typically not required in type 2 diabetes until beta cell failure occurs, if it does.

Fortunately, if you have type 2 diabetes, you may potentially be able to control your blood sugar and prevent further disease progression with lifestyle measures alone.


LADA (Latent Autoimmune Diabetes in Adults) is a slow, progressive form of autoimmune diabetes that occurs in adults (13, 14).

Sometimes people are misdiagnosed as having type 2 diabetes when they actually have LADA, especially if they are overweight or have other risk factors for type 2.

If you were diagnosed with type 2 diabetes but your blood sugar levels remain very high despite following a healthy diet and taking oral diabetes medication as prescribed, it is possible that you have LADA.

This can be verified by a blood test that checks for antibodies that attack your pancreatic beta cells. In addition, your doctor can order a c-peptide test to measure how much insulin your pancreas is producing.

Importantly, if you have LADA, you will need to inject insulin, regardless of the diet you follow and how much exercise you get.

However, as with type 1 diabetes, making changes to your diet can help reduce your insulin dosage.

Gestational diabetes

Gestational diabetes occurs only in pregnancy as a result of weight gain and hormonal fluctuations that happen during this time.

However, although all women experience these changes during pregnancy, only about 1-14% develop gestational diabetes (15).

Pregnant women are screened for gestational diabetes by taking an oral glucose tolerance test midway through their pregnancy. If diabetes is confirmed, treatment typically includes both lifestyle modification and diabetes medication or insulin.

Although their blood sugar levels often normalize after delivery, women who have had gestational diabetes are 7 times more likely to develop type 2 diabetes than women who haven’t had the condition (16).

Regardless of the type of diabetes you have, there are evidence-based lifestyle strategies that can significantly improve your blood sugar control and may even increase your quality of life.

Risk factors you can change and those you can’t

Although anyone can develop diabetes, certain risk factors significantly increase your own odds. Some of these you have no control over; however, many can be substantially reduced by making lifestyle changes.

Risk factors you can’t change


Certain genetic mutations (differences in gene sequences) are associated with increased diabetes risk.

Although evidence is still emerging in this area, scientists recently identified specific mutations that may be responsible for pancreatic beta cell destruction in type 1 diabetes and impaired glucose and insulin regulation in type 2 diabetes (17 , 18).

In addition, a strong family history of type 2 diabetes is a major risk factor for developing the disease.

In fact, if one of your parents has type 2 diabetes, you have a 40% increased risk of developing it. If both parents have type 2 diabetes, the risk increases to 70% (19).

Some rare forms of diabetes have a strong genetic component, including Maturity Onset Diabetes in the Young (MODY). Although it accounts for only 1-2% of all cases of diabetes, people who inherit the MODY genetic mutation have a 95% risk of developing the disease at some point in their lifetime (20).

Ethnic background

You may be at increased risk for diabetes based on your race and geographic location.

For instance, Caucasian people of European descent have a greater likelihood of developing type 1 diabetes than other ethnic groups (21).

By contrast, type 2 diabetes occurs more frequently in Hispanics,

African-Americans, Indians and certain Asian populations than in Caucasians (22).


Type 2 diabetes risk increases with age. People over 45 are much more likely to get type 2 diabetes than younger individuals.

Researchers have shown that this is mainly due to increased insulin resistance and other age-related metabolic changes that occur around midlife (23).

Indeed, the longer you live, the greater your chances of developing diabetes or prediabetes.

In the US alone, up to 33% of people over 65 have diabetes and 50% are believed to have prediabetes (24).

Previous chemical exposure

Emerging evidence suggests that exposure to toxins may play a role in the development of both type 1 and type 2 diabetes.

These include plastics, air pollution, cigarette smoke and other chemicals that you may have been exposed to earlier in life (25, 26).

However, further high-quality studies in this area are needed.

Risk factors you can change

Although risk factors for type 1 diabetes are largely beyond your control, there are many things you can do to reduce your risk for type 2 diabetes, which is far more common.

Abdominal obesity

Being obese significantly increases the likelihood that you will be diagnosed with type 2 diabetes at some point. However, not everyone who is obese will develop type 2 diabetes.

Additionally, where you carry excess fat is much more important than your actual weight.

Studies have shown that increased belly fat, also known as visceral fat, is a major diabetes risk factor. Having too much fat in the abdominal cavity causes inflammation and drives insulin resistance (27, 28, 29).

Large waist size is a strong predictor of diabetes risk. A large waist is defined as 35 inches (89 cm) or more for a woman and 40 inches (102 cm) or more for a man.

One study looking at data from over 26,000 people found that obese men with large waists were 22 times more likely and obese large-waisted women nearly 32

times more likely to get diabetes than men and women of normal weight and waist size (29).

Taking steps to lose excess belly fat can greatly reduce your risk for diabetes.

Sedentary lifestyle

Sitting too much and moving too little can increase your odds of developing type 2 diabetes (30).

One large analysis of 47 studies found that people who spent the greatest number of hours engaged in sedentary behaviors had a 91% increased risk of developing diabetes (31).

Fortunately, the reverse seems to be true as well. People who perform exercise and engage in regular activity tend to have a lower diabetes risk.

What’s more, a study in people with prediabetes suggests that working out regularly may even improve beta cell function, helping to reduce disease progression (32).

To reduce diabetes risk, reversing sedentary behavior is key.

Poor-quality diet

Eating foods and beverages high in sugar and refined carbs may do more than cause weight gain.

Studies have consistently linked this eating pattern to greater insulin resistance, higher blood sugar levels and increased odds of developing type 2 diabetes and other diseases (33, 34, 35).

On the other hand, avoiding refined carbs, eating more whole foods and reducing overall carb intake may significantly reduce diabetes risk (36, 37).


It’s well known that smoking increases risk for lung cancer and heart disease. However, you may not realize that it also places you at greater risk for type 2 diabetes.

Cigarette smoking has been found to increase both the odds of getting diabetes and the likelihood of developing diabetes-related complications, including foot and limb amputations (38, 39).

A large analysis of several studies found that smoking increased the risk of developing diabetes by a whopping 61% in heavy smokers, defined as smoking more than 20 cigarettes per day (40).

Fortunately, tobacco-related diabetes risk may be completely reversible if you quit early enough. One study in middle-aged men who stopped smoking found that after 20 years, these men had the same risk of developing diabetes as people who had never smoked (41).

The take home message here is that rather than focusing on the risk factors you can’t control, it’s important to work on changing the ones that you can.

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